This research project is directed towards a further understanding of the membrane structures involved in the control of ionic permeabilities that are responsible for excitation in nerve and muscle. We seek to identify and characterize specific reactive groups closely associated with these structures. Single neurons under voltage clamp are exposed to group-specific reagents either externally or via internal perfusion, and changes in kinetic and steady state properties are measured. We hope to ultimately develop a procedure whereby a radioactive analog of such a reagent can be used to label important groups and allow further biochemical analysis. We have studied a class of sulfhydryl blocking compounds that inactive sodium channels in an unusual manner, and are now examining some proteolytic enzymes, and trypsin in particular, that have just the opposite effect. We are also concerned with the mechanism of action of volatile general anesthetics, and are testing theories involving changes in lipid fluidity as a mechanism of action. We hope that the results of this research will ultimately lead to a better understanding of the mechanism of action of a number of neuropharmacological agents.